1. Field of the Invention
The present invention relates to an image forming apparatus and system. More particularly, the present invention relates to an image forming apparatus and system in which the image qualities of images to be output by the image forming apparatus are predicted from the evaluation data of test images (internally prepared pattern images) and image forming conditions are adjusted on the basis of the data to produce high quality images. In addition, the present invention also relates to an image forming condition adjusting method, a computer program for carrying out the image forming condition adjusting method, and a recording medium for storing the computer program.
2. Discussion of the Background
Recently, there is an increasing need for high-speed complex image forming apparatus in which conventional facsimile machines, copiers and printers are combined and in which images are formed at a high speed while effectively using a network.
In attempting to stably produce high quality images using such complex image forming apparatus, techniques such that a test image is internally formed in an image bearing member such as photoreceptors and intermediate transfer media; the average reflectivity or image density of the test image is measured using a detector such as photosensors; and the image forming conditions are adjusted on the basis of the measurement data are known. In addition, techniques such that an image is practically formed on a recording medium such as papers; the image qualities of the output image are evaluated; and the image forming conditions are adjusted on the basis of the measurement data, to prevent formation of abnormal images such as fine character images with low resolution caused by deterioration of the developer used, are also known.
Published unexamined Japanese patent application No. (hereinafter referred to as JP-A) 2002-040725 discloses a technique in that a test image is formed on an image bearing member; the image density thereof is measured with a detector such as photosensors; it is determined whether the image density falls in a desired range; and the image forming conditions are adjusted on the basis of the measurement data to prevent formation of abnormal images such as fine character images with low resolution caused by deterioration of the developer used.
JP-A 2001-215761 discloses a technique in that a test image is formed on an image bearing member; the amount of the toner in the test image is measured with a detector such as photosensors; and the current of the transfer bias is adjusted on the basis of the measurement data.
JP-A 05-313453 discloses a technique in that test images (such as dot images and line images) having different areas are formed on an image bearing member; the image densities of the test images are measured with a detector such as photosensors; and image forming conditions are adjusted on the basis of the measurement results, to prevent production of images with low resolution.
In the measurement methods described in JP-As 2002-040725, 215761 and 05-313453 mentioned above, the average reflectivity or image density of toner images formed on a photoreceptor or an intermediate transfer medium is measured with a photosensor and the process conditions are adjusted on the basis of the measurement data to prevent formation of abnormal images. However, the reflectivity and image density tend to be influenced by characteristics of the photoreceptor and intermediate medium (hereinafter referred to as image bearing members). For example, when the materials or lots of such image bearing members are changed, it is often necessary that service men change the reference values of the reflectivity and image density.
It is well known that granularity, clearness and gradation property of images are very important image qualities. Among these image qualities, only the gradation property is evaluated on average and process conditions are adjusted on the basis of the evaluation data in the techniques mentioned above. Namely, variation of the gradation property in a one or two dimensional direction is not considered. In addition, deterioration of the granularity and clearness is not considered in these techniques, i.e., the process conditions are not adjusted while considering granularity and clearness.
JP-A 2002-214865 discloses a technique in that image forming conditions of an image outputting device are detected; the detection data are sent to an image processing apparatus; the controlling device of the image processing apparatus controls the image forming conditions of the image outputting device on the basis of the sent image forming conditions, to stably produce desired images.
In this technique, images to be evaluated are formed on a recording material such as papers and process conditions are adjusted depending on the evaluation data. Therefore, the running costs increase. In addition, when an output instruction is made by an apparatus other than the image processing apparatus, which is connected with the output device through a network, the controlling device of the image processing apparatus does not have an ability to select a proper output device or a proper image processing method. Namely, the system cannot make good use of the apparatuses connected through a network.
On the other hand, a large number of images are output by the above-mentioned high-speed image forming apparatus, and thereby a large amount of waste developer is produced. Therefore, there is a probability that the waste developer causes environmental pollution. In attempting to avoid such a problem (i.e., to effectively use the developer), current image forming apparatus typically adopt a toner recycling system in which particles of the developer (toner) remaining on the image bearing member are collected by a cleaning device and the collected developer particles are fed to the developing device to be reused.
JP-A 2001-7222197 discloses a technique in that image qualities are predicted on the basis of data concerning the mixing ratio of the recycled developer particles to virgin developer particles; and the time at which the developer is to be replaced with a virgin developer is informed, to reduce the running costs of the output device and to increase the operational efficiency of the output device.
In this technique, image qualities are predicted on the basis of only the developer mixing ratio data, i.e., image qualities of a real image are not evaluated. Since the characteristics of a developer greatly change depending on environmental conditions, there is a probability of occurrence of a problem in that the replacement time at which the developer is to be replaced with a virgin developer comes earlier than the predicted replacement time. Alternatively, there is a probability that the developer used has to be replaced with a virgin developer even when the developer has no problem.
JP-A 2001-358941 discloses a technique in that the image qualities of images output by an image forming apparatus are evaluated; the evaluation data, which are repeatedly obtained, are stored in a memory, which is connected with a network, to accumulate data; and an image processing apparatus selects a proper image processing method on the basis of the evaluation data.
In this technique, images to be evaluated are formed on recording materials such as papers and process conditions are adjusted on the basis of the evaluation data. Therefore, the running costs increase. In addition, when an output instruction is made by an apparatus other than the image processing apparatus through a network, it is difficult to select a proper output device. Namely, the system cannot make good use of the apparatuses connected through a network.
Because of these reasons, a need exists for an image forming apparatus and system capable of producing high quality images without abnormal images using a method in which a toner image formed on an image bearing member is evaluated without using receiving materials and the image forming conditions are adjusted on the basis of the evaluation data while considering granularity, clearness and gradation property of images.